1. Field of the Invention
The present invention relates to an apparatus for bioelectrical impedance measurements for determining body composition data of the human body and to a corresponding method.
2. Discussion of the Prior Art
The conductivity of a human body is strongly influenced by its water content. Since areas of the body which are free of fat, such as muscles and bodily fluids, contain the major part of the water content of the body, while on the other hand fat tissue has a relatively low water content, the determination of the conductivity of a body or of a body segment (or the determination of the reciprocal resistance or impedance of the body or of the body segment) allows to draw conclusions on the relative fat content, at least if further data such as body height and weight of the person are taken into account.
A method and an apparatus for bioelectrical impedance analysis are described for example in WO 97/01303. The apparatus described therein comprises eight electrodes, namely four electrodes for the feet, in each case two electrodes for contacting one foot, and four hand electrodes, in each case two electrodes for contacting one hand of the person. An alternating current is applied through two electrodes which are positioned on different limbs, and the voltage between two other electrodes is measured, which measuring electrodes are likewise positioned on different limbs. By switching over to two other current applying electrodes and voltage measuring electrodes different body segments can be examined consecutively. Furthermore, when current is injected in one hand and in one foot, and voltage is measured between the other electrode on the same hand and the other electrode on the same foot, one side of the body as a whole can be measured.
If all electrodes on hands and feet are in electrical contact with their respective body member, a plurality of measuring programs or configurations is available, namely configurations as to which electrodes act as current applying electrodes and which act as voltage measuring electrodes. These configurations of current applying electrodes and voltage measuring electrodes determine which body segments is measured or whether the body as a whole is measured. If two electrodes are in electrical contact on each of the four limbs, a number of possible measuring programs is available. If electrodes are used which are attached by adhesive means there may be cases in which certain measuring programs are omitted if this allows to use fewer electrodes. In addition there are situations in which the person to be examined can not have all four limbs in contact with electrodes, for example if one limb is amputated or is covered by a dressing or plaster cast. In such situation the person to be examined will establish contact with the measuring apparatus with those limbs which are available for contacting the electrodes. Then the person to be examined or assisting personnel has to select the measuring program that is to be carried out. As mentioned above this may include, depending on the number of contact points, one or more possible measuring programs.
In EP 2 042 843 A1 it was proposed to arrange a bioelectrical impedance measuring apparatus in such a manner that the bioelectrical impedance measuring unit is switched on if it is found that at least two electrodes of the apparatus are in contact with the person to be examined, or is otherwise turned off if less than two electrodes are found to be in contact.